The present invention relates to a process for obtaining CCM (Catalyst Coated Membranes) composites equipped with subgaskets on each side, to be used in electrochemical cells.
The composite of the present invention comprises a membrane formed of (per)fluorinated ionomers.
Composites formed of membranes having catalyst coated surfaces are known in the prior art. Said composites are generally known with the name Catalyst Coated Membrane or CCM. The two CCM electrocatalytic layers form respectively the positive electrode and the negative electrode of the electrochemical cell. Electrocatalytic layer means a layer containing a metal having the property to act as catalyst of the reaction which takes place in the cell semielement wherein there is the electrode.
For the use in electrochemical devices, in particular in fuel cells, the membrane with the electrocatalytic layers is assembled with layers for the gas diffusion, by placing at least one of said layers on each CCM side. Said diffusion layers are contacted with bipolar plates, which separate the single cells, thus forming electrical series. The obtained assembly is also called fuel cell stack.
The CCM surface fraction which is involved in the electrochemical reaction is called as active area. The above gas diffusion layers, applied to the catalyst coated membrane, have the purpose to protect the CCM integrity when contacted with the bipolar plates, and furthermore to assure the reactant feeding and the reaction water discharge.
The use of protective films, formed by inert materials towards the reaction taking place in the electrochemical device is known in the prior art. These protective films are known as subgaskets. The films are generally applied on both sides of the MEA device composite with the purpose of improving the handling thereof, rendering easier for example the assembly in the electrochemical devices. Further, the subgaskets protect the polymeric electrolyte from the contact with the bipolar MEA plates. The subgasket covers the nonactive area of the device and therefore has a central empty space in correspondence of the active area. A CCM with the subgasket is reported in FIG. 1, wherein (2′) represents the subgasket and (1′) the active area.
Therefore a CCM with subgasket is generally formed of the following parts:                an internal layer formed of an ionomeric membrane;        two surface layers, one on each side of the internal layer and symmetrically placed, composed of the following parts:        an active area, generally placed in the central position of the surface layer;        a subgasket (2′) delimiting the active area (FIG. 1).        
The need was felt to have available a continuous process for obtaining CCM assemblies as above, having a subgasket on each of the two surfaces.